British officials are not commenting on why Australian euthanasia advocate Philip Nitschke was detained at London's Gatwick Airport for several hours overnight.

Upon arrival Dr Nitschke says he was called out by name and escorted to a room where various items he uses for his workshops were taken away.

He says eventually they were returned and he was allowed entry to the UK after a delay of several hours.

Dr Nitschke believes opponents of his work, including religious and disability organisations, may have sparked his brief detention.

"There are issues about terrorism and other things that require good border protection, but I wouldn't have thought giving people end-of-life choices comes into that category," he said.

The first of his workshops will be held in London on Tuesday then in Dublin on Saturday, where previous meetings have been disrupted by anti-euthanasia protesters.

Dr Nitschke says he was shocked when an immigration official told him he should not have been surprised at his detention because of what he does.

"I was a little taken aback by that statement because what I do is lobby for changing the law on voluntary euthanasia and giving people choices," he said.

"If that means that every time you come into a country like Britain it means you're going to be taken out of the queue, have officers waiting for you, be paged off the plane and then searched thoroughly because of what I do, it's a little bit disappointing."

He says although he was carrying test kits and demonstration items, he was not carrying any drugs or prohibited items.

"We were taken down into the basement of Gatwick airport. All of our luggage has been gone through," he said.

"A number of items have been taken away for inspection.

"They include bits and pieces used at workshops, flow regulators and the like, associated with the euthanasia pieces of equipment that we use as demonstration."